body {
    font-family: sans-serif;
    line-height: 1.6;
    margin: 0;
    padding: 0;
    background-image: url('fondo.jpg'); 
    background-size: cover;
    background-position: center center;
    background-repeat: no-repeat;
    background-attachment: fixed; 
    color: #333;
    min-height: 100vh; 
    display: flex; 
    flex-direction: column;
}

#background-video {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    object-fit: cover;
    z-index: -1;
}

header {
    background: rgba(45, 55, 72, 0.9);
    color: #fff;
    padding: 10px 20px;
    display: flex;
    align-items: center;
    justify-content: center;
    position: sticky;
    top: 0;
    z-index: 1000;
    min-height: 60px;
    box-sizing: border-box;
    flex-shrink: 0;
    position: relative;
}

#header-actions {
    display: flex;
    align-items: center;
    position: absolute;
    right: 20px;
    top: 50%;
    transform: translateY(-50%);
}

#logo-container {
    text-align: center;
    width: 100%;
}
#logo-img { height: 80px; width: auto; display: inline-block; }
nav#menu-principal {
    text-align: right;
    position: absolute;
    left: 20px;
    top: 50%;
    transform: translateY(-50%);
}
nav#menu-principal button, nav#menu-principal span,
#btn-notificaciones {
    margin: 5px 0 5px 10px;
    padding: 8px 15px;
    background-color: #4A5568;
    color: white;
    border: none;
    cursor: pointer;
    border-radius: 5px;
    font-size: 0.9em;
    transition: background-color 0.3s ease, transform 0.2s ease;
}
nav#menu-principal button:hover,
#btn-notificaciones:hover {
    background-color: #2D3748;
    transform: translateY(-1px);
}
nav#menu-principal span { background-color: transparent; color: #E2E8F0; cursor: default; font-weight: bold; padding-right: 0; }

/* Botón para menú hamburguesa */
#hamburger-btn {
    display: none;
    background: none;
    border: none;
    color: #fff;
    font-size: 1.6em;
    cursor: pointer;
    margin-left: 10px;
}

#btn-notificaciones {
    position: relative;
    margin-left: 10px;
}
.contador-notificaciones {
    position: absolute;
    top: -6px;
    right: -6px;
    background-color: #E53E3E;
    color: white;
    border-radius: 50%;
    padding: 2px 6px;
    font-size: 0.7em;
    line-height: 1;
}

main#contenedor-principal {
    padding: 20px;
    flex-grow: 1;
    display: flex;
    flex-direction: column;
    justify-content: center; /* Centrado vertical */
    align-items: center;    /* Centrado horizontal */
}
footer { text-align: center; padding: 20px; background: rgba(26, 32, 44, 0.85); color: #A0AEC0; flex-shrink: 0; }

.vista { display: none; padding: 25px; background-color: rgba(255, 255, 255, 0.97); border-radius: 8px; box-shadow: 0 6px 25px rgba(0,0,0,0.25); margin-bottom: 25px; width: 100%; box-sizing: border-box; }
.vista.activa { display: block; }

#vista-bienvenida {
    display: flex; flex-direction: column; justify-content: center; align-items: center;
    flex-grow: 1; text-align: center; background-color: transparent; 
    box-shadow: none; border-radius: 0; padding: 20px; position: relative; 
    box-sizing: border-box; margin-bottom: 0; 
}

#vista-bienvenida .texto-bienvenida {
    background-color: rgba(255, 255, 255, 0.92);
    padding: 30px 35px;
    border-radius: 12px;
    margin-bottom: 40px;
    max-width: 680px;
    /* width: auto;  Quitamos 'width: auto;' o 'display: inline-block;' si estaba. */
    /* display: inline-block;  <--- QUITAR ESTO SI ESTÁ */
    box-shadow: 0 8px 25px rgba(0,0,0,0.2);
    text-align: center;
    box-sizing: border-box;
    margin-left: auto;
    margin-right: auto;
    /* Por defecto, un div es display: block, lo cual está bien para un ítem flex en una columna */
}

#vista-bienvenida .texto-bienvenida p { margin: 0 0 18px 0; font-size: 1.15em; color: #1A202C; line-height: 1.75; }
#vista-bienvenida .texto-bienvenida p:first-child { font-weight: bold; font-size: 1.25em; color: #2D3748; }
#vista-bienvenida .texto-bienvenida p:last-child { margin-bottom: 0; }

/* Botón principal en la bienvenida - YA TIENE SU ESTILO ÚNICO .boton-grande */
#vista-bienvenida .boton-grande {
    /* Los estilos de padding, font-size, etc. se mantienen */
    /* display: inline-block; ya lo tenías y está bien para este botón en sí mismo,
       pero su centrado lo maneja el align-items: center del padre #vista-bienvenida */
    margin-left: auto;
    margin-right: auto;
}
#vista-bienvenida .boton-grande:hover {
    background-color: #2F855A; transform: translateY(-3px) scale(1.02); 
    box-shadow: 0 8px 20px rgba(0,0,0,0.25);
}
#vista-bienvenida .boton-admin { position: absolute; bottom: 25px; right: 25px; padding: 8px 15px; font-size: 0.85em; background-color: rgba(45, 55, 72, 0.7); color: #E2E8F0; border: 1px solid rgba(255,255,255,0.3); border-radius: 5px; cursor: pointer; transition: background-color 0.3s ease, color 0.3s ease; }
#vista-bienvenida .boton-admin:hover { background-color: rgba(26, 32, 44, 0.9); color: white; }

/* Vistas de Formularios y Dashboard (general) */
#vista-login-admin, #vista-login-alumno, #vista-registro-alumno,
#vista-anadir-libro, #vista-gestionar-libro-propio, #vista-dashboard {
    max-width: 700px;
    margin-left: auto;
    margin-right: auto;
}

#vista-login-alumno, #vista-registro-alumno {
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
}
#vista-dashboard { max-width: 980px; }

#vista-login-admin h3, #vista-login-alumno h3, #vista-registro-alumno h3, 
#vista-anadir-libro h3, #vista-gestionar-libro-propio h3 {
    text-align: center; color: #1A202C; margin-top: 0; margin-bottom: 30px; font-size: 1.8em;
}
form label { display: block; margin-bottom: 8px; font-weight: 600; color: #2D3748; }
form input[type="email"], form input[type="password"], form input[type="text"], 
form input[type="file"], form select {
    width: 100%; padding: 12px; margin-bottom: 20px; border: 1px solid #A0AEC0;
    border-radius: 5px; box-sizing: border-box; font-size: 1em; background-color: #FFFFFF;
}
form input[type="email"]:focus, form input[type="password"]:focus, form input[type="text"]:focus,
form input[type="file"]:focus, form select:focus {
    border-color: #3182CE; box-shadow: 0 0 0 3px rgba(49, 130, 206, 0.4); outline: none;
}

/* === ESTILO BASE UNIFICADO PARA BOTONES DE ACCIÓN PRINCIPALES === */
.boton-accion-base {
    padding: 10px 18px; /* Ajustado para consistencia */
    color: white;
    border: none;
    border-radius: 6px; /* Unificado */
    cursor: pointer;
    margin-right: 10px; /* Margen común */
    font-weight: bold;
    font-size: 1em;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    transition: background-color 0.3s ease, transform 0.2s ease, box-shadow 0.2s ease;
    box-shadow: 0 2px 4px rgba(0,0,0,0.15);
    display: inline-block; 
}
.boton-accion-base:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(0,0,0,0.2);
}

/* Colores específicos para botones que usan .boton-accion-base */
.boton-accion-base.submit, /* Para botones de submit de formularios */
form button[type="submit"] { /* Para compatibilidad con estilos anteriores */
    background-color: #3182CE; /* Azul */
}
.boton-accion-base.submit:hover,
form button[type="submit"]:hover {
    background-color: #2B6CB0; 
}

.boton-accion-base.cargar, /* Para "Cargar Libro" */
#btn-ir-anadir-libro { /* ID específico del botón Cargar Libro */
    background-color: #38A169; /* Verde */
}
.boton-accion-base.cargar:hover,
#btn-ir-anadir-libro:hover {
    background-color: #2F855A; 
}

.boton-accion-base.gestionar, /* Para "Gestionar" en tarjeta y "Editar" en vista gestión */
.libro-card button.btn-gestionar-libro,
#btn-editar-libro-info {
    background-color: #DD6B20; /* Naranja */
}
.boton-accion-base.gestionar:hover,
.libro-card button.btn-gestionar-libro:hover,
#btn-editar-libro-info:hover {
    background-color: #C05621;
}

.boton-accion-base.eliminar, /* Para "Eliminar" en vista gestión */
#btn-eliminar-libro {
    background-color: #E53E3E; /* Rojo */
}
.boton-accion-base.eliminar:hover,
#btn-eliminar-libro:hover {
    background-color: #C53030;
}

.boton-accion-base.pedir, /* Para "Pedir" */
.libro-card button.btn-pedir-prestado,
.item-lista-libro .acciones button.btn-solicitar-devolucion {
     background-color: #38A169; /* Verde */
}
.boton-accion-base.pedir:hover,
.libro-card button.btn-pedir-prestado:hover,
.item-lista-libro .acciones button.btn-solicitar-devolucion:hover {
    background-color: #2F855A;
}

.boton-accion-base.devolver, /* Para "Devolver" */
.libro-card button.btn-marcar-devuelto,
.item-lista-libro .acciones button.btn-marcar-devuelto {
    background-color: #3182CE; /* Azul */
}
.boton-accion-base.devolver:hover,
.libro-card button.btn-marcar-devuelto:hover,
.item-lista-libro .acciones button.btn-marcar-devuelto:hover {
    background-color: #2B6CB0;
}

/* Para "Solicitar Devolución" reutiliza el color del botón ".pedir" */
.boton-accion-base.solicitar-devolucion,
.btn-solicitar-devolucion {
    background-color: #38A169; /* Verde */
}
.boton-accion-base.solicitar-devolucion:hover,
.btn-solicitar-devolucion:hover {
    background-color: #2F855A;
}
.boton-accion-base.info { background-color: #3182CE; }
.boton-accion-base.info:hover { background-color: #2B6CB0; }

/* Botones secundarios de formulario (grises, como "Volver", "Cancelar") */
form button[type="button"] { 
    padding: 10px 15px; 
    background-color: #A0AEC0; 
    color: white;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    margin-right: 10px;
    font-weight: 500; 
    transition: background-color 0.3s ease, transform 0.2s ease;
}
form button[type="button"]:hover { 
    background-color: #718096; 
    transform: translateY(-1px);
}

#alumno-avatar-registro { font-size: 1.2em; } 
#libro-foto-preview { max-width: 200px; max-height: 200px; border: 1px solid #ddd; margin-top: 5px; margin-bottom: 15px; object-fit: cover; background-color: #fff; }

/* ESTILOS PARA EL DASHBOARD COMPLETO */
#vista-dashboard h2 { color: #1A202C; text-align: center; margin-bottom: 10px; }
#vista-dashboard > p { text-align: center; font-size: 1.1em; color: #2D3748; margin-bottom: 15px; }
/* El botón #btn-ir-anadir-libro ahora usa .boton-accion-base.cargar */
#vista-dashboard > button#btn-ir-anadir-libro { display: block; margin-left: auto; margin-right: auto; margin-bottom: 25px; }
#vista-dashboard hr { border: none; height: 1px; background-color: #CBD5E0; margin-top: 25px; margin-bottom: 25px; }
#vista-dashboard h3 { color: #2D3748; text-align: left; margin-bottom: 20px; margin-top: 10px; font-size: 1.5em; }
.seccion-dashboard { margin-bottom: 30px; }
.lista-dashboard-libros, .lista-solicitudes { display: flex; flex-direction: column; gap: 15px; }
.lista-notificaciones { display: flex; flex-direction: column; gap: 10px; }
.item-notificacion {
    background-color: #edf2f7;
    padding: 8px 12px;
    border-radius: 5px;
    color: #2D3748;
}
.item-notificacion.nueva { font-weight: bold; }
.boton-visto-notificacion {
    background-color: #E2E8F0;
    color: #2D3748;
    border: none;
    border-radius: 4px;
    padding: 3px 8px;
    font-size: 0.75em;
    margin-left: 8px;
    cursor: pointer;
}
.boton-visto-notificacion:hover {
    background-color: #CBD5E0;
}
.lista-novedades { display: flex; flex-direction: column; gap: 15px; }
.item-novedad { display: flex; align-items: flex-start; }
.item-novedad .icono-novedad { margin-right: 8px; }
.item-lista-libro, .item-solicitud { display: flex; align-items: flex-start; background-color: #f8f9fa; padding: 12px; border-radius: 6px; border: 1px solid #e2e8f0; box-shadow: 0 2px 4px rgba(0,0,0,0.05); }
.item-lista-libro img.thumbnail, .item-solicitud img.thumbnail { width: 60px;  height: 85px; object-fit: cover; border-radius: 4px; margin-right: 15px; flex-shrink: 0; }
.item-lista-libro .detalles, .item-solicitud .detalles { flex-grow: 1; font-size: 0.95em; display: flex; flex-direction: column; gap: 4px; }
.item-lista-libro .detalles strong, .item-solicitud .detalles strong { display: block; font-size: 1.1em; font-weight: 600; color: #2D3748; margin-bottom: 2px; }
.item-lista-libro .detalles span, .item-solicitud .detalles span { display: block; color: #4A5568; font-size: 0.85em; }
.item-lista-libro .acciones, .item-solicitud .acciones { margin-left: 15px; flex-shrink: 0; display:flex; flex-direction:column; gap: 5px; }
/* Los botones dentro de .acciones ahora usarán .boton-accion-base y su color específico */
.item-lista-libro .acciones button, .item-solicitud .acciones button { 
    padding: 7px 14px; 
    font-size: 0.8em; 
    width: 100%;
}

/* Tarjetas de Libros (para la lista general "Libros Disponibles") */
.libro-card {
    background-color: rgba(255, 255, 255, 0.98); border: 1px solid #e2e8f0;
    border-radius: 8px; padding: 10px; margin: 8px; width: 190px; min-height: 300px;
    display: flex; flex-direction: column; justify-content: space-between;
    box-shadow: 0 4px 6px -1px rgba(0,0,0,0.1), 0 2px 4px -1px rgba(0,0,0,0.06);
    text-align: center; transition: transform 0.2s ease-in-out, box-shadow 0.2s ease-in-out;
}
.libro-card:hover { transform: translateY(-3px); box-shadow: 0 10px 15px -3px rgba(0,0,0,0.1), 0 4px 6px -2px rgba(0,0,0,0.05); }
.libro-portada { width: 100%; height: 180px; object-fit: cover; border-radius: 4px; margin-bottom: 8px; background-color: #e2e8f0; }
.libro-titulo {
    font-size: 1.05em; font-weight: 600; color: #1A202C; margin-bottom: 8px;
    display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical;
    overflow: hidden; text-overflow: ellipsis; height: 2.5em; line-height: 1.25em;
}
.libro-propietario, .libro-estado { font-size: 0.8em; color: #4A5568; margin-bottom: 0; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.libro-meta { display:flex; justify-content:space-between; align-items:center; gap:4px; margin-bottom:6px; }
.libro-info-prestamo { font-size: 0.8em; color: #c05621; background-color: #fffaf0; padding: 6px; border-radius: 4px; margin-top: 5px; margin-bottom: 6px; line-height: 1.3; border: 1px dashed #dd6b20; }
.libro-card button { margin-top: auto; width: 100%; box-sizing: border-box; }
/* Los botones btn-pedir-prestado, btn-gestionar-libro, btn-marcar-devuelto en .libro-card USARÁN .boton-accion-base y su modificador de color */

.libro-card.no-disponible {
    filter: grayscale(1);
    opacity: 0.6;
}

#lista-libros-disponibles { display: flex; flex-wrap: wrap; justify-content: center; gap: 15px; padding-top: 15px; }
#btn-ver-mas { margin: 20px auto; display: block; }

.filtros-libros { display: flex; flex-wrap: wrap; gap: 10px; margin-bottom: 15px; align-items: center; }
.filtros-libros input,.filtros-libros select { padding: 6px; }

/* Estilos para Login Visual de Alumnos */
.contenedor-avatares { display: flex; flex-wrap: wrap; justify-content: center; gap: 20px; margin-bottom: 30px; padding: 10px; }
.avatar-seleccionable { display: flex; flex-direction: column; align-items: center; padding: 15px; border: 3px solid transparent; border-radius: 10px; cursor: pointer; transition: border-color 0.2s ease, transform 0.2s ease, background-color 0.2s ease; min-width: 90px; text-align: center; background-color: #f8f9fa; }
.avatar-seleccionable:hover, .avatar-seleccionable.seleccionado { border-color: #3182CE; transform: scale(1.08); background-color: #e9ecef; }
.avatar-seleccionable .avatar-emoji { font-size: 3.5em; margin-bottom: 8px; text-shadow: 0 2px 3px rgba(0,0,0,0.1); }
.avatar-seleccionable .avatar-nombre-display { font-size: 0.9em; color: #2D3748; font-weight: 500; }
#vista-login-alumno #avatar-seleccionado-nombre { text-align: center; font-size: 1.5em; font-weight: bold; margin-bottom: 20px; color: #1A202C; }
#vista-login-alumno #form-login-alumno-pin { border-top: 1px solid #e2e8f0; padding-top: 25px; margin-top: 20px; }
#vista-login-alumno #seleccion-login-registro-alumno button { margin-bottom: 10px;}

.link-button { 
    background: none!important; border: none; padding: 5px !important; 
    color: #3182CE; text-decoration: underline; cursor: pointer; 
    font-size: 0.95em; font-weight: 500; display: inline-block; margin-top: 5px;
}
.link-button:hover { color: #2B6CB0; transform: none!important; }

/* Colores para aceptar/rechazar usando clases generales */
.boton-accion-base.aceptar { background-color: #38A169; }
.boton-accion-base.aceptar:hover { background-color: #2F855A; }

@media (max-width: 768px) {
    .item-lista-libro, .item-solicitud { flex-direction: column; align-items: center; text-align: center; }
    .item-lista-libro .acciones, .item-solicitud .acciones { flex-direction: row; margin-left: 0; margin-top: 10px; }
    .libro-card { width: 45%; }

    /* Navegación responsive */
    nav#menu-principal { display: none; }
    nav#menu-principal button,
    nav#menu-principal span { display: none; }
    #hamburger-btn { display: block; }
    nav#menu-principal.mobile-open {
        display: flex;
        flex-direction: column;
        position: absolute;
        right: 20px;
        left: auto;
        top: 60px;
        background: rgba(45, 55, 72, 0.95);
        padding: 10px;
        border-radius: 8px;
        width: 160px;
    }
    nav#menu-principal.mobile-open button,
    nav#menu-principal.mobile-open span { display: block; margin: 8px 0; text-align: left; }
}


@media (max-width: 480px) {
    .libro-meta { flex-direction: column; align-items: flex-start; }
    .libro-card { width: 100%; }
}


.lista-ranking { list-style: decimal; padding-left: 20px; }
.lista-ranking li { margin-bottom: 5px; }

#popup-notificaciones {
    position: absolute;
    right: 0;
    top: calc(100% + 5px);
    display: none;
    background-color: #fff;
    border: 1px solid #CBD5E0;
    border-radius: 6px;
    box-shadow: 0 4px 10px rgba(0,0,0,0.15);
    width: 260px;
    max-height: 300px;
    overflow-y: auto;
    padding: 10px;
    z-index: 1500;
}
#popup-notificaciones .item-notificacion { margin-bottom: 8px; }
#popup-notificaciones .item-notificacion:last-child { margin-bottom: 0; }

#popup-mensaje {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    display: none;
    background-color: rgba(0,0,0,0.6);
    align-items: center;
    justify-content: center;
    z-index: 2000;
}

#popup-mensaje .contenido {
    background-color: #fff;
    padding: 20px;
    border-radius: 8px;
    box-shadow: 0 4px 12px rgba(0,0,0,0.2);
    max-width: 320px;
    text-align: center;
    position: relative;
}
#popup-mensaje .contenido button {
    margin-top: 10px;
}

#epub-viewer {
    width: 100%;
    height: 500px;
    margin-top: 10px;
}

/* Visualizador PDF */
.pdf-viewer {
    width: 100%;
    max-height: 500px;
    overflow: auto;
    margin-top: 10px;
    border: 1px solid #CBD5E0;
}
.pdf-viewer canvas {
    width: 100%;
    height: auto;
    display: block;
}
.error-pdf {
    color: red;
    padding: 10px;

}